SIM card
(Subscriber Identity Module card) A smart card that gives a cellphone its phone number and customer identity. Introduced in 1991 for GSM phones, most cards are removable. Satellite and LTE phones also use SIM cards. Activated by the cellular carrier, the SIM card contains a unique ID, authentication codes, network-specific data and the customer's phone contacts. See IMSI.
As long as users stay with the same carrier, they can generally switch their phone number and calling plan to a different phone by moving the SIM card. For travelers, prepaid SIM cards are available for unlocked phones, and phones that hold more than one SIM are also offered (see multi-SIM). In the early 1990s when cellphones were large, the first SIMs were the size of a credit card (1FF). See eSIM, SIM lock, R-UIM and smart card.
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| Mini, Micro and Nano SIM Cards |
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| A SIM is a chip with contacts on cardboard. Used during the transition from Mini to Micro cards, Micro SIMs were placed in a Mini SIM form factor (right). |
Size Thick Form SIM Card (mm) (mm) Factor
Full Size 86x54 .76 1FF
Mini (Standard) 25x15 .76 2FF
Micro 15x12 .76 3FF
Nano 12x9 .67 4FF
Embedded 6x9 up to 1
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| Mini SIM |
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| This Mini SIM was removed and flipped over to show the contacts and the six pins they press against. |
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| Open the Case or Slide Out the Tray |
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| Access to a SIM card is either from the inside by taking the back off or by inserting a pin into the side of the phone that releases the tray. See SIM needle. |
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| Prepaid SIM Cards |
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| For travelers with unlocked Android and other GSM cellphones, prepaid SIM cards can be purchased. |
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| Mini or Micro |
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| A SIM card may come in both Mini and Micro SIM formats that can be punched out as required. |
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